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  <a href="http://sudopedia.enjoysudoku.com/Bivalue_Universal_Grave.html">BUG+2</a>
  <p>
  	If <b>candidate {0}</b> was removed from the <b>cells {1}</b> each unsolved cell would have two candidates and each candidate would occur exactly twice in each row, column and block.<br/>
  	A Sudoku showing this so-called BUG (Bivalue Universal Grave) has either zero or two solutions rendering the puzzle invalid.<br/>
    Extra candidates in one of the unsolved cells are needed to avoid this <a href="http://sudopedia.enjoysudoku.com/Deadly_Pattern.html">deadly pattern</a>. 
  </p> 
  <p>
  	<b>{1}</b> are the only cells with an extra candidate: <b>digit {0}</b>.<br/>
	To avoid the deadly pattern at least one of the <b>{2} cells</b> must contain the <b>value {0}</b>.<br/>
	Therefore none of the cells seen by all <b>{2} cells</b> can contain the <b>digit {0}</b> as candidate.
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